British industrialist Sanjeev Gupta has unveiled an ambitious plan for a “grand-scale steel plant” in Whyalla, capable of annual exports of 10 million tonnes.

The billionaire on Monday revealed details of what he said could become one of the world’s largest steel production facilities.

Chinese company China Metallurgical Group Corporation has signed on to build the new facility for Mr Gupta’s company, GFG Alliance, if it gets final approval.

Mr Gupta also outlined a $600 million expansion of the South Australian city’s steel mill to lift production to 1.8 million tonnes each year.

He was joined in Whyalla on Monday by Prime Minister Scott Morrison, Opposition Leader Bill Shorten and SA Premier Steven Marshall as he spoke of his vision to grow and secure thousands of jobs.

Mr Gupta said when he first came to the city with a view to taking over the troubled steelworks, his briefing notes suggested a rescue was not possible.

“This was the poor cousin, a broken steel town,” he said.

“But those of you who know me know that’s like red rag to a bull.”

Mr Gupta joins steelworkers on a march on the day his company took over the factory. Photo: AAP

Mr Gupta said what he actually found was a “diamond” and a company with a workforce that was willing to fight. In 2016, Whyalla steelworkers voted to take a 10 per cent pay cut to help ensure the factory’s survival.

At the time, the steelworks was being administered by KordaMentha. Partner Mark Mentha said he had he prepared himself for the most complex administration job in Australia’s corporate history when he arrived in Whyalla.

“Six thousand employees, four billion of debt … a business that had 70 per cent of the Australian structural steel market could disappear overnight. When you look into the eyes of the employees, that’s where you see the vulnerability and the fear,” he told the ABC in 2016.

It became very obvious that this town, this great community of Whyalla, wanted to save itself.”

The pay cuts were controversial, but eventually won the approval of a narrow majority of the steelworks’ employees.

On Monday, Mr Morrison described Whyalla – which is about a four-and-a-half-hour drive from Adelaide – as the comeback city of Australia with a bright future in investment and jobs.

“This is the turnaround state and this is the comeback city in Australia when we’re talking about Whyalla,” the PM said.

While Mr Marshall said there was a growing confidence that Whyalla’s best days for manufacturing lay ahead.

On a day of what local authorities described as “transformational announcements”, the city council said other new projects would include a $45 million hotel, a $145 million horticulture facility and a $6 million organic recycling business.

It’s been suggested the expansion of steel production and the other developments will boost Whyalla’s population from about 20,000 to about 80,000.

Mr Marshall said Whyalla had got itself back on track.

“It wasn’t that long ago that people thought the days of manufacturing were well behind us in Australia,” he said.

“What we’re seeing here in Whyalla is our best days for manufacturing are here in front of us.”

-with AAP